IEM Daily Bulletin for Jun 12 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 12 June 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jun 11 9:55 AM	iem,main	🐛 Fix bugs with (un)rectify_wfo	Link
Jun 11 10:10 AM	pyiem,main	💥 Migrate IEM web template to bootstrap 5	Link

Daily Feature

June Precipitable Water + Rainfall
Date: 11 Jun 05:30 AM
Votes: Good: 16   Bad: 1 Abstain: 0

Using an offline archive the IEM maintains of NWS forecast model grid point output for airport locations in Iowa, the featured chart takes a fun look comparing precipitable water (PW) and precipitation frequency. PW is a depth measure of the amount of liquid equivalent water that's in a column of atmosphere. Rewording, if all the water (in its various phases) were squeezed out of the atmosphere as liquid, how much rain would fall. So the plot compares this PW value based on the NWS NAM model with the same day calendar day rainfall total for Des Moines during the month of June. Please note that the model value is valid at 7 AM. We find a rather direct and intuitive relationship. As the atmosphere loads up with water, the frequency of observed rainfall increases! The overall climatology is around 40%, so PW values of around 1.25 inches and lower tend to have a higher frequency of dry days vs climatology. The bottom panel compares the 7 AM PW value with the same calendar day precipitation. The one-to-one line nicely shows that the PW value is often an upper bound to precipitation, but it is certainly not a hard limit and things like training thunderstorms can replenish PW during rainfall events. PW values will be on the increase this week, particularly over northern Iowa and support some significant rainfall events.

NWS Watch/Warning Summary for 12 AM 11 Jun 2025 - 12 AM 12 Jun 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	5	0	0	0	0	0	0	0
Svr Tstorm	85	23	2	4	11	0	6	2
Flash Flood	20	0	0	0	0	0	0	---

ARX = LaCrosse, WI DVN = Davenport, IA DMX = Des Moines, IA OAX = Omaha, NE FSD = Sioux Falls, SD

IEM Cow Report

SVR+TOR Warnings Issued:  87 Verified:  32 [36.8%]
Polygon Size Versus County Size            [18.7%]
Average Perimeter Ratio                    [21.6%]
Percentage of Warned Area Verified (15km)  [16.8%]
Average Storm Based Warning Size           [1622 sq km]
Probability of Detection(higher is better) [0.70]
False Alarm Ratio (lower is better)        [0.63]
Critical Success Index (higher is better)  [0.32]